The present invention, relates to grinding systems, and more specifically to methods and apparatus for automatically sharpening blades on cutting reels of lawn mowers.
Commercial reel-type lawn mowers typically utilize cutting reels that have helical blades. The cutting reels must be maintained regularly to assure proper operation. Part of such maintenance involves sharpening the blades and sharpening and/or adjusting the bed knives. The sharpening process typically involves two steps. The first step involves spin grinding the tips or radially outer ends of the blades in order to true the reel back to cylindrical shape and sharpen the cutting edge. The second step involves relief grinding the trailing edge of each blade.
U.S. Pat. No. 5,321,912 to Neary et al. teaches a grinding system for spin and relief grinding cutting reels of commercial reel-type lawn mowers. The Neary et al. grinding system utilizes a common rotating drive shaft to rotate a spin grinding wheel and a relief grinding wheel. Both grinding wheels are separately axially slideably mounted on the common rotating shaft, which is generally parallel to the axis of the cutting reel to be ground. While the Neary et al. system offers the common rotating shaft, which is a desirable feature to many grinder operators, it lacks a means of auto indexing from blade to blade. Thus, the Neary et al. grinding system requires an operator to manually cycle each blade through the relief grinding process. This is labor intensive and time consuming. In addition, the fork assemblies 32 on either side of the grinding wheels necessarily wear from sliding contact with the grinding wheels and/or grinding shaft 18, and they provide poor positioning stability for the grinding wheels.
U.S. Pat. No. 6,010,394 to Dieck et al. teaches a grinding system for spin and relief grinding cutting reels of commercial lawn mowers. The Dieck et al. grinding system utilizes a movable grinding head, which includes a grinding wheel and a motor mounted on a carriage. The grinding head is slideably mounted on rails that are generally parallel to the axis of the cutting reel. The Dieck et al. system offers an auto indexing system for automatically indexing from blade to blade.
There is a need in the art for a grinding system that allows auto indexing on a grinding system utilizing a common rotational shaft, reduces part friction and wear, and improves grinding accuracy.
The present invention, in one embodiment, is a device for relief grinding a blade having a radially outer edge of an elongated length and first and second faces, with the first and second faces extending generally radially from a reel axis. The device includes a rotatable grinding shaft, a grinding wheel, a grinding wheel guide assembly, a guide finger, and a first non-sliding stabilizer.
The rotatable grinding shaft defines a grinding wheel axis. The grinding wheel is rotatable with and axially slideable along the grinding shaft to follow the elongated length of the blade. The grinding wheel includes a hub with a first bearing surface. The grinding wheel guide assembly is mounted for motion parallel to the grinding wheel axis on at least one rail that extends the elongated length of the blade and is substantially parallel to the grinding wheel axis. The guide finger is adjustably supported on the grinding wheel guide assembly for contacting one face of the blade during grinding and holding the blade in position for relief grinding. The first non-sliding stabilizer bearing is supported on the grinding wheel guide assembly for bearing contact with the first bearing surface. The first stabilizer bearing is oriented to apply to the first bearing surface forces applied to the grinding wheel guide assembly that include a component parallel to the grinding wheel axis.
The present invention, in another embodiment, is a device for relief grinding a blade having a radially outer edge of an elongated length and first and second faces, with the first and second faces extending generally radially from a reel axis. The device includes a rotatable grinding shaft, a grinding wheel, a grinding wheel guide assembly, a guide finger, and a first non-sliding stabilizer bearing.
The rotatable grinding shaft defines a grinding wheel axis. The grinding wheel is rotatable with and axially slideable along the grinding shaft to follow the elongated length of the blade. The grinding wheel includes a hub with a stabilizer bearing surface. The grinding wheel guide assembly is mounted for motion parallel to the grinding wheel axis on at least one rail that extends the elongated length of the blade and is substantially parallel to the grinding wheel axis. The guide finger is adjustably supported on the grinding wheel guide assembly for contacting one face of the blade during grinding and holding the blade in position for relief grinding. The first non-sliding stabilizer bearing is interposed for bearing contact between the grinding wheel guide assembly and the stabilizer bearing surface. The first stabilizer bearing is oriented to apply to the stabilizer bearing surface forces applied to the grinding wheel guide assembly including both a component parallel to the grinding wheel axis and a component perpendicular to the grinding wheel axis.
While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention. As will be realized, the invention is capable of modifications in various obvious aspects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive.